[MEncoder-users] how to test encoded file ?

[Grozdan]

On Thu, Jul 8, 2010 at 12:27 PM, Bernd Butscheidt <bbutscheidt at yahoo.de> wrote:
> From: Grozdan <neutrino8 at gmail.com>
> 7. July 2010, 23:04:27 h
>
>
>>Why do you use -mc 0?
>
>
> Well, I tried to fix problems which occured with an HDTV record. I catched this
> somewhere in the web. I can play the source with mplayer but the reencode always
> gets out of sync. It didn't help...  mc0 is still in my script though, up to
> now, it didn't hurt but it has no meaning so far.

-mc 0 should only be used as last resort if during normal encode
without it, you get sync issues. If you don't get such, there's not
point in forcing -mc 0 all the time because, as said, it can lead to
problems even on proper input files

>
>
>>and why do you want to create a true 24 fps film file?
>
> I just like to have back the original speed (movie at 24 fps)

So the original was true film? Not 23.976fps?

>
>
>>Still, if you want 24fps file, use -vf
>>filmdint=fast=0/io=25:24/dint_thres=256 -ofps 24
>
> I haven't discovered this yet. But will this just drop frames to achieve 24fps
> or slow down the movie (which means reverse the PAL-Speedup?) Anyway, maybe this
> is out of topic anyway.

IIRC, it interpolates, doesn't drop them to achieve this. If you want
to maintain pitch and all, use -af scaletempo. Note that filmdint only
accepts for the 'io' option integer values, so you can't do something
like io=25:23.976 in filmdint. Also, you can't do the revers, going
from lower fps to higher fps.

>
>
>>Also, your file will be broken since you haven't disabled b-frames in
>>your x264 line (which are on by default) and you're using the lavf
>>muxer to output which is broken with b-frames + mencoder
>
> Yes, it is broken, but an avi-File with 24fps and x264-codec isn't well
> supported too. As I said, I remux the "broken" output with mkvmerge and
> everybody (vlc, mplayer, xine and my LG BD350 Stand alone Blue Ray Player) is
> happy and reports

It doesn't have to be supported. You encode to avi and when done, you
use mkvmerge for mkv. Even if your players play it, there's no
guarantee at some point you won't get a file that won't be playable.
And since the surroundings of mencoder keep changing while mencoder
remains the same and isn't updated to support newer changes, at some
point bigger issues could arise (or it may even stop working, who
knows?)

>
> a) that the file is 24fps
> b) a longer movie length compared to the PAL source, which was the goal.
>
> Maybe I still get something wrong, but so far it seems to work.
>
> So back to the question:
> My humble way to test x264-encoding with mencoder is to use the broken lavf
> muxer (with mkv), because you don't get trouble with output greater than 4GB.
> The first test can be done with mplayer which can handle the broken files at
> least so well that you get a proper idea about the video quality. To fix the
> broken muxing of lavf, I use mkvmerge which makes the file playable anywhere
> else.

Actually, you shouldn't test with mplayer, because mplayer itself has
bugs and will happily play the broken file which will lead you to
conclude all is fine, while in reality it may not be. Always use one
or more other players to check how the file is

>
> Kind regards
> Bernd
>
>
>
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